Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $86.25   11.151%   $95.8677   $95.87   $95.85   $95.90  
  Purchase #2 $236.93   7.108%   $253.771   $253.77   $253.75   $253.80  
  Purchase #3 $95.88   8.607%   $104.1324   $104.13   $104.15   $104.10  
  Purchase #4 $93.54   3.423%   $96.7419   $96.74   $96.75   $96.70  
  Purchase #5 $117.28   11.166%   $130.3755   $130.38   $130.40   $130.40  
  Purchase #6 $95.63   9.683%   $104.8899   $104.89   $104.90   $104.90  
  Purchase #7 $241.48   4.699%   $252.8271   $252.83   $252.85   $252.80  
  7 purchase totals = $966.99       $1,038.6055   $1,038.61   $1,038.65   $1,038.60